De magnatize

[Randall Va]

drilled a hole in a mag. in lathe chuck,now my chuck is magnatized,anyone know how to de magnatize it?
Thanks Randall

[Doug4d3s]

You need to expose it to a coil of a single conductor (not an extension cord) that an AC current is flowing through, and then slowly move the coil away.

I'm going to make something to do this myself, as I posted about it a while back. I think I can make something myself cheaper than I can order anything sold to do this.

Also I haven't liked the ones that I've seen advertised, they all are made to sit on a tabletop. I need a wand type-thing I can wave around easily where I need it.........
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[Randall Va]

Thanks Doug
When you get it made would like to know how it works

[jim rozen]

A bulk tape eraser will do this too.

Jim

[Doug4d3s]

Well my first two experiments are a bust, but I'm getting closer....

The first was about 35 turns of #18 speaker wire wraped around a wood dowel; that did not visibly work at all. I ran this through a 35-watt lamp for a load.

Next I found a bit of #22 bell wire (transformer-winding wire), that was maybe a couple hundred turns on a plastic spool; this will make the magnetic chips vibrate, but only the smaller ones fall free. The bell wire does not get hot though.

Now I have found another 1-lb spool of bell wire... This is #26, unused (none missing from the spool) and figures out to be around 4,450 turns of wire on the spool. Will try this next.... At least this shouldn't need anything else to limit the current.

TV degaussing coils I'm seeing online don't seem to have that many turns; maybe a few hundred if they use finer wire, #26+.

If anybody watching has a real degaussing coil (and can see) what's the wire size and about how many turns does it use?...
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[jim rozen]

Do you have a Weller soldering gun?

Jim

[chipswarf]

I haven't made, or tried one of these things, but I'd like to suggest larger coils, so that the chuck can pass through the center. A small diameter coil does give you an oscillating field, but it's localized and drops off quickly without much 'penetrating' the chuck. Intuitive rather than analytical, I know.

Mark

[steamin10]

Around the machine shop that made the tools for my presses, they were always doing a demag, especially after ginding on a magnet table. On punching hole, just alittle magnetism holds the punchouts and shearing scrap at the hole. The being a negatine effect on clearing th parts and tool wear. The Demag coil they used was homemade, and the throat big enough to pass tools through the center. It was made of 500 ft of #14 wire around a 4x 6 box of thin plywood glued together without metal in it. It was shaped like a trough all round, and was regular solid house wire. It was plugged in, and the parts hand passed through the center several times and set aside. The guass field set up,pretty much erased any magnetics locked in the steel. It amazed me that the wire being a direct short, did not pop a breaker. The energy created a field that damped the current, but it ws never left on for mare than a minute or two either.

[Doug4d3s]

... It was made of 500 ft of #14 wire ... It amazed me that the wire being a direct short, did not pop a breaker....

This is the hard part.
I know the lightbulb was sucking a lot of power, but I don't have any books around that tell easy ways to roughly detirmine the impedance of a design. I have read that once you get up above 400 or so turns of bell wire, that is enough that you won't need anything to limit the wall current. I don't know what the figure would be for regular lamp or speaker wire, as nobody normally winds inductors from it.

Another way I heard to demagnetize a TV screen was to get a very strong small magnet, stick it on a drill bit and use a drill to spin the bit+magnet. That should work for this also (I would think) but some of the chips would fly over and end up stuck to the magnet tho'...

Ya'd want a big loop to put around the lathe chuck, but you'd also want something small to run down the lathe bore......
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[gunboatbay]

The previous recommendation about the tape demagnetizer is the easiest & best solution. These were made to demagnetize the old reel-type music tapes, are quite powerful and work great for most sizes of items you want to demagnetize, including large chucks. I bought this one on ebay for $5 plus shipping and it solved all my problems:

[jim rozen]

If you have a weller gun, replace the tip with a large loop of copper wire. If you can make it ten turns or
so, that's better. But the turns can't touch each other, and it may get warm so it probably should be
bare copper wire. The ground wire from NM cable, number 12 size, works well.

Make the loop large enought to fit around the chuck.

Put it over the chuck, energize the gun.

Sweep the loop back and forth over the gun. Keep the
gun energized the entire time.

While keeping the trigger down, pull the loop as far away from the
chuck as you can, slowly. Only after it is more than several
feet away, can you let off the gun trigger.

Should do the job.

Jim

[Doug4d3s]

Well still no love.

First off--I went back and measured the spools of wire I was using, to find the number of turns on the first one. The winding area on the spools are 2-5/16" wide and a bit over a half-inch deep. These are 1-lb spools when full.

The first #22 spool I was using, I made a big error in estimating the turns.... it is a quarter-inch deep (which is about half full) and that works out to around 750 turns.... I would not have guessed it was that many. The second #26 spool is full, and is somewhere around 4,600 turns. I also have a 60-watt light hooked in series with the coils.

The 750-turn coil worked way better than the 4600-turn coil did.

I also tried hooking the 750-turn coil straight to the wall current, and it was much stronger but very quickly got hot (and I mean, like in three seconds!). In ten seconds it would have been on fire.

I'm going to try a larger coil diameter next, maybe six inches or so. The strongest part of the magnetic field is in the center of the coil (or very near the edge) and so the coil has to be big enough to put stuff inside it.

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This makes me wonder more and more what the tape demagnetizers are doing to limit current. A transformer can be left plugged in with no load on it, but a transformer has a metal core that offers some loading all on its own.
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